physiological and biochemical responses of eight eucalyptus species to salinity stress

theeffect of salt stress on the pysiological and biochemical responses of the seedlings of eight eucalyptus species viz. e. kingsmillii, e. tetragona, e. salubris, e. occidentali, e. microtheca, e. camaldulensis, e. globules and e. sargentii was analyzed. four month-old seedlings grown in greenhouse were watered by five levels of salt solution (0, 50, 100, 150 and 200 mm of nacl) in five replications with a factorial experimental design. the results indicated that salinity delayed and inhibited the seedlings’ growth after one month, and induced gradual decline in most of the criteria such as leaf area, relative water content and specific leaf area. moreover, a significant reduction of chlorophyll a, b and total chlorophyll content was observed. salinity stress raised the content of soluble sugars, proline and glycine betaine. eucalyptus sargentii as the most tolerant species had the optimum growth up to 200 mm nacl but e. globulus presented the most sensitive speciesto salinity stress. at 200 mm nacl, proline and glycine beatine raised to 10.57 and 27 µg g-1 in the tolerant species (e. sargentii), respectively while proline in the sensitive species (e. globulus) dropped to 0.003 µg g-1. these results suggest that high tolerance of e. sargentii to salinity stress is closely related to lower specific leaf area and enhancement of compatible solutions such as proline, soluble sugar, glycine beatine. this would encourage the possibility of propagating e. sargentii in the southern coastal area of iran. furthermore, these results provided further biochemical support for the specific abiotic stress tolerance mechanism of eucalyptus species.